Modeling and Experimental Studies of Miniature Lithium Air Batteries and Alkaline Direct Ethanol

339 Pages·2017·7.43 MB·English

by  Jing Huang

University of Connecticut
OpenCommons@UConn
Doctoral Dissertations University of Connecticut Graduate School
8-18-2015
Modeling and Experimental Studies of Miniature
Lithium Air Batteries and Alkaline Direct Ethanol
Fuel Cells
Jing Huang
University of Connecticut - Storrs, [email protected]
Follow this and additional works at:https://opencommons.uconn.edu/dissertations
Recommended Citation
Huang, Jing, "Modeling and Experimental Studies of Miniature Lithium Air Batteries and Alkaline Direct Ethanol Fuel Cells" (2015).
Doctoral Dissertations. 887.
https://opencommons.uconn.edu/dissertations/887
Modeling and Experimental Studies of Miniature Lithium Air Batteries and Alkaline
Direct Ethanol Fuel Cells
Jing Huang, PhD
University of Connecticut, 2015

Batteries and fuel cells directly convert chemical energy to electricity through controlled
electrochemical reactions. Batteries also serve as energy storage devices, while fuel cells rely on
a continuous supply of fuel to maintain power output. In this dissertation, modeling and
experimental studies on lithium air batteries and alkaline direct ethanol fuel cells are presented.
Both technologies can be designed as small-scale electrochemical devices that are suitable for
miniature electronics and energy systems. Innovative concepts are presented regarding
miniaturization of both technologies, including detailed physical simulation. The lithium air (Li-
air) battery is considered a promising candidate for next generation secondary battery technology
because of its extremely high theoretical energy density. Its application, however, has been
impeded by issues including electrode clogging, electrolyte degradation, low cycling efficiency,
and safety concerns. A unique Li-air battery concept is proposed to enhance oxygen supply and
alleviate electrode clogging. The proposed flow cell has a specific capacity of 15.5 times higher
than that of a conventional Li-air cell. Based on the physical modeling, a multi-layer electrode
structure is also proposed which helps to increase cell capacity by 105%. A comprehensive 2D
physical model of the battery is developed at the cell-level. Through the deformed mesh technique,
the change of electrolyte level in a Li-air coin cell during discharge is tracked. It is found that
without considering this effect, a battery model may underestimate cell capacity by up to 22%.
The model also includes an air chamber in the computation domain to account for solvent
evaporation. For highly volatile solvent-based cells, the chamber size may affect the experimental
results significantly. These findings provide direction for further enhancement of battery
Jing Huang – University of Connecticut, 2015
performance and better design of experiments. Alkaline direct ethanol fuel cells (ADEFC) are
considered as a replacement of direct methanol fuel cells. The alkaline environment improves
reaction kinetics while ethanol is well regarded for wide availability and low toxicity. Through
detailed modeling and experimental studies, it is shown that the costly anion exchange membrane
in a conventional ADEFC can be replaced by a much less expensive porous separator without
lowering overall cell performance.
Modeling and Experimental Studies of Miniature Lithium Air Batteries and Alkaline Direct
Ethanol Fuel Cells

Jing Huang

B.S., Xi’an Jiaotong University, 1999
M.S., Xi’an Jiaotong University, 2002

A Dissertation
Submitted in Partial Fulfillment of the
Requirements for the Degree of
Doctor of Philosophy
at the
University of Connecticut

2015
Copyright by
Jing Huang

2015

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University of Connecticut
2015
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Acknowledgements
In the past four and half years, I received countless help from my advisor, professors, lab-mates
and family. I would like to express my deepest appreciation here.
First and foremost I want to thank my advisor Dr. Amir Faghri. It has been an honor to be able
to work under his direction. His vision, encouragement, and patience have helped me to learn how
to be a better researcher and present high quality works. Dr. Faghri always encourages me to think
out of box, which I will keep in my mind forever.
I also want to express my thanks to my co-advisors, Dr. Fan, Dr. Lu, Dr. Mustain and Dr.
Pasaogullari for their insightful advices during my PhD study.
During my stay in the heat transfer lab, I shared a lot of times with my lab mates. I would like
to express my appreciation for helpful discussions with them.
Finally I would like to thank my parents for their consistent support and understanding.

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Table of Contents
Table of Contents ............................................................................................................................ v
List of Tables ................................................................................................................................. xi
List of Figures ............................................................................................................................... xii
Chapter 1 A Critical Review of Modeling Studies on Li–O2 and Li–Air Batteries: Challenges
and Opportunities ........................................................................................................ 1
Background ................................................................................................................. 1
Development of continuum-scale physical models ..................................................... 4
1.2.1 Model formulation ........................................................................................... 4
1.2.2 Features of existing models ............................................................................. 9
1.2.3 Cathode modeling .......................................................................................... 11
1.2.4 Anode modeling ............................................................................................. 22
1.2.5 Special features of continuum-scale models .................................................. 24
Particle-scale and multi-scale models ....................................................................... 33
Property data .............................................................................................................. 34
1.4.1 Fundamentals ................................................................................................. 36
1.4.2 Summary of property data ............................................................................. 37
1.4.3 Discussion ...................................................................................................... 38
Unresolved issues and future opportunities ............................................................... 42
Concluding remarks .................................................................................................. 43
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References ........................................................................................................................... 47
Tables .................................................................................................................................. 62
Figures................................................................................................................................. 74
Chapter 2 Modeling study of a Li-O2 battery with an active cathode ........................................ 87
Introduction ............................................................................................................... 87
Existing models ......................................................................................................... 90
Model development ................................................................................................... 92
2.3.1 Governing equations ...................................................................................... 93
2.3.2 Boundary conditions ...................................................................................... 98
Results and discussion ............................................................................................. 101
2.4.1 Model validation .......................................................................................... 101
2.4.2 Distributions of pressure, velocity and temperature .................................... 102
2.4.3 Compare the capacity to conventional Li-O2 battery .................................. 103
2.4.4 Discharge capacities of passive vs. active batteries ..................................... 104
2.4.5 Distribution of lithium ion and oxygen ....................................................... 105
2.4.6 Effect of pressure difference between channels .......................................... 106
2.4.7 Effect of exchange current density .............................................................. 107
2.4.8 Effect of porosity ......................................................................................... 107
Conclusions ............................................................................................................. 109
References ......................................................................................................................... 111
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Tables ................................................................................................................................ 116
Figures............................................................................................................................... 117
Chapter 3 Capacity Enhancement of a Lithium Oxygen Flow Battery ................................... 132
Introduction ............................................................................................................. 132
Background ............................................................................................................. 134
Model development ................................................................................................. 137
3.3.1 Governing equations .................................................................................... 138
3.3.2 Electrochemical Kinetics ............................................................................. 144
3.3.3 Boundary and initial conditions ................................................................... 145
Results and discussion ............................................................................................. 147
3.4.1 Model validation .......................................................................................... 147
3.4.2 Parametric study .......................................................................................... 148
3.4.3 Energy consumption by electrolyte pump ................................................... 153
3.4.4 Capacity enhancement using dual layer cathode ......................................... 154
3.4.5 Capacity enhancement using alternating flow ............................................. 155
Conclusion ............................................................................................................... 156
References ......................................................................................................................... 160
Tables ................................................................................................................................ 166
Figures............................................................................................................................... 169
Chapter 4 Analysis of Electrolyte Level Change in a Li–Air Battery ..................................... 180
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